The present invention relates generally to a resin composition possessing an antistatic property that is not practically lowered by washing or wiping, and more particularly to an antistatic resin composition comprising a multiply grafted or multilayer graft copolymer alone or a mixture of the multiply grafted copolymer and a thermoplastic resin compatible therewith, the multiply grafted copolymer comprising a core non-elastic or hard resin layer, an intermediate rubbery or elastic graft layer comprising an elasticity-imparting monomer selected from conjugated dienes and acrylates and a polyalkylene oxide monomer, and an outermost non-elastic or hard resin layer.
In general, plastics have high electrical resistance and tend to be easily charged with static electricity due to friction or peeling. For this reason, plastics are liable to attract dust and dirt, resulting in various troubles such as impairment of the appearances of shaped articles, sheets, films and fibers formed from these plastics.
Methods for imparting antistatic property to such plastics that are susceptible to static electricity have been investigated and can be roughly classified as follows.
1. Methods which involve kneading an antistatic agent into plastics. PA1 2. Methods which involve applying an antistatic agent (surfactant) over the surface of plastics. PA1 3. Methods which involve applying a silicone compound over the surface of plastics. PA1 4. Methods which involve chemically reforming the molecular structure of plastics.
Of these methods, a method which involves kneading an antistatic agent into plastics cannot successfully impart a permanent antistatic effect, and, when the antistatic agent present over the surface of the plastics is removed by washing with water or rubbing, the antistatic effect is lost.
Further, if an antistatic agent bleeds excessively over the surface of plastics, dust and dirt adhere thereonto.
Since the antistatic agent must be present over the surface of a shaped article obtained from plastics in appropriate quantity, shaping or processing conditions will be extremely limited.
The method which involves applying a surfactant over the surface of plastics requires a step of uniformly applying the surfactant over the surface of a shaped plastic article, and further the surfactant is easily removed by washing or rubbing whereby the antistatic effect is drastically impaired.
The method which involves chemically reforming the molecular structure of plastics by introducing hydrophilic groups into plastics by polymerization and the like generally requires the introduction of a considerable quantity of hydrophilic groups in order to obtain a high antistatic effect, so that the mechanical and other properties of the plastics deteriorate because of the increased hygroscopicity thereof.
In the course of our research on processes for producing resins possessing permanent antistatic property that is not lowered by washing, we obtained a rubber trunk polymer having a low specific volume resistivity. We further found that a graft copolymer obtained by graft-polymerizing a vinyl or vinylidene monomer onto the rubber trunk polymer alone or a mixture of this graft copolymer and a resin compatible therewith has a permanent antistatic effect, and that a copolymer comprising 1 to 50% (by weight, as in all percentages and parts set forth hereinafter) of a monomer comprising 4 to 500 alkylene oxide groups and 50 to 99% of an acrylate is suitable as the rubber trunk polymer (U.S. Patent Ser. No. 72,846, l Masaki OHYA et al.).